Vol. 65.] 



IHE CAULDEON -SUBSIDENCE OF GLEN COE. 



649 



can once more be ascertained with certainty. For a short space, 

 indeed, as may be seen from the sketch-map (fig. 6), the fault-line 

 serves as the boundary between mica-schist striking north-north- 

 east and quartzose ' Moine ' gneisses striking north-west. With the 

 latter occur scattered outcrops of pale grey lavaform rhyolite asso- 

 ciated with patches of sedimentary-looking breccia, both of which 

 appear to be restricted to the southern side of the fault. The 

 northern side is the home of the fault-intrusion, which, at one point, 

 extends in a tongue along the dislocation, and is clearly chilled 

 against an outcrop of the rhyolite. 



No appearance of special shearing has been noticed in the 

 vicinity of the fault-line in this Stob Beinn a' Chrulaiste section, 

 but it must be remembered that much of the ground is very obscure. 



Stob Mhic Mhartuin (fig. 7). — For a mile west of Stob 

 Beinn a' Chrulaiste the country is too thickly littered with moraines 



Fk 



7. — Map of Stob Mhic Mhartuin (north-north-east dykes 

 omitted). 



\%&\fault intrusion 



EARLY FAULT 

 I INTRUSION 



I B> \ breccia PATCH 



\MOINE GNEISSES 



/.AQUARTZITE 



DIP OP BEDDING 

 VERTICAL BEDDING 

 PAUL TS 



to furnish evidence regarding the boundary-fault. In Stob Mhic 

 Mhartuin, however, the complex features of this disturbance are 

 illustrated with a clearness which is almost diagrammatic. This 

 hill makes a prominent feature near General Wade's military road, 

 where the latter follows the zigzag ascent out of Glen Coe known 

 as The Devil's Staircase : and the section is eas)^ of access, since a 

 grassy slope leads up to it from the main road on the floor of 

 the Glen. 



The rocks at the foot of the low frontal cliff of the Stob, that is, 

 on the southern or inner margin of the boundary-fault, are well- 

 bedded quartzites. They are vertical, and have a uniform north- 

 north-westerly strike, like the other schists of the neighbourhood 

 within the faulted area. Preliminary signs of trouble, however, 

 are not wanting. Several narrow zones of shearing are en- 

 countered crossing the quartzite in a west-north-westerly direction, 



